How often can you do core training?

I have been working on core strengthening to shore up a dodgy back. I generally lift 2 times per week and do core training at that time. I always take a day off between lifting days. My question pertains to core training. Can I do core training every day? Things like planks, situps, & other core strengthening work. Thanks, Dave

I get most of my back issues when I go on backpacking trips with my son's Scouting group. I'm fine until I take off the pack and then stretch out to rest on my bedroll. That's when I get spasm's in my lower back.